1. Technical Field of the Invention
The present invention relates generally to a bi-fuel engine for vehicles which runs on two types of fuel: one is liquid fuel, and the other is gas fuel.
2. Background Art
Bi-fuel engines designed to run on two types of fuel: one being liquid fuel such as gasoline, and the other being gas fuel such as compressed natural gas (CNG), are known as internal combustion engine for automotive vehicles. A typical one of such bi-fuel engines is equipped with a gas fuel injection device disposed on a cylinder head cover mounted on the top of an engine body and gas fuel hoses connecting gas fuel injectors of the gas fuel injection device and an intake manifold together. The gas fuel hoses extend beneath a liquid fuel injection device.
For example, Japanese Patent First Publication No. 2010-242559 teaches such a type of bi-fuel engine.
The above structure in which the gas fuel injection device and the gas fuel hoses are arranged on the top of the cylinder head cover, however, faces drawbacks, as discussed below. The removal of the cylinder head cover from the engine body requires steps of dismounting the liquid fuel injection device, disconnecting the intake manifold from the gas fuel injection device, uninstalling the gas fuel injection device, and disconnecting the gas fuel pipes from the intake manifold. The assembly or disassembly of the engine is, therefore, quite inconvenient.
Additionally, the gas fuel injection device is located close to the intake manifold. The total length of the gas fuel hoses connecting between the gas fuel injection device and the intake manifold is, therefore, short. It is, thus, difficult to bend the gas fuel hoses to lay out and joint them to the engine.
Moreover, the gas fuel injection device is mounted over the top of the cylinder head cover, so that it greatly protrudes outside the cylinder head cover. The exertion of external force on the vehicle may, thus, result in physical interference of the gas fuel injection device with peripheral devices.
Further, when an air cleaner is disposed above the engine, it may interfere with the gas fuel injection device which projects greatly from the cylinder head cover. The air cleaner is, thus, subjected to the restriction on volume thereof.